The present invention relates to a process for simultaneously passivating organochlorosilane reactor fines and generating values therefrom.
As shown in U.S. Pat. No. 4,500,724, methylchlorosilane reactor fines (hereinafter sometimes "silicon-containing fines") may be generated during the synthesis of methylchlorosilanes by the reaction of powdered silicon with methyl chloride, usually in the presence of a copper catalyst. Some of the generated fines are recycled, while others are discarded. As discussed in U.S. Pat. No. 5,274,158, a serious discarded fines management problem can occur with respect to build-up and disposition, as these materials are often pyrophoric. Silicon-containing fines can have an average particle size of about 0.1 to about 200 microns with at least 2% copper by weight in the elemental or chemically combined state.
As shown in the aforementioned U.S. Pat. No. 5,274,158, a procedure which can be used to render pyrophoric silicon-containing fines substantially non-reactive in air is to subject them to a heat treatment in an inert atmosphere at a temperature in the range of about 900.degree.-1500.degree. C.
Early studies also showed that SiCl.sub.4 and HSiCl.sub.3 can be made by contacting metallurgical grade silicon powder and HCl in the presence of a copper catalyst at about 300.degree. C. Higher temperature are known to favor the exclusive formation of SiCl.sub.4. Although various procedures are known for passivating discarded silicon-containing fines to render them more manageable, interest also has been shown in developing techniques for both salvaging and passivating silicon-containing fines to derive some of the silicon and metallic values from the discarded finely divided silicon contact mass.